Underwater heat sink

ABSTRACT

A cryogenic heat sink is described in association with underwater breathing apparatus of the cryogenic oxygen supply type. The heat sink is characterized by utilization of oxygen absorbent material to generate a low pressure on a body of liquid oxygen, the low pressure being regulated by a pressure responsive valve, so that the liquid oxygen vaporizes to seek an equilibrium condition between vapor and liquid states at a single predetermined constant temperature.

United States Patent 1191 Rem [ UNDERWATER HEAT SINK [75] Inventor: Charles R. Rein, Panama City, Fla.

[73] Assignee: The United States of America as represented by the Secretary of the Navy, Washington, DC,

22 Filed: Nov. 14, 1973 21 Appl. No.: 415,907

[52] US. Cl 62/48, 62/50, 62/52, 128/142.2, 128/203 [51] Int. Cl. Fl7c 11/00 [58] Field of Search 62/48, 50,51, 52; 128/1422, 203

[56] References Cited 7 UNITED STATES PATENTS 2,322,617 6/1943 Dayhuff 62/48 3,366,107 1/1968 Frantom 128/142.2

[ Feb. 4, 1975 3,386,458 6/1968 Wasserman et a] 128/142.2 X 3,570,481 3/1971 Woodberry, Jr l28/l42.2 3,807,396 4/1975 Fischel .i 128/142 Primary Examiner-Meyer Perlin Assistant Examiner-Ronald C. Capossela Attorney, Agent, or FirmRichard S. Sciascia; Don D. Doty; Harvey A. David [57 ABSTRACT A cryogenic heat sink is described in association with underwater breathing apparatus of the cryogenic oxygen supply type. The heat sink is characterized by utilization of oxygen absorbent material to generate a low pressure on a body of liquid oxygen, the low pressure being regulated by a pressure responsive valve, so

that the liquid oxygen vaporizes to seek an equilibrium condition between vapor and liquid states at a single predetermined constant temperature.

4 Claims, 2 Drawing Figures PATENTEU 4|975 FIG. '1'

UNDERWA TEE BREA THING APPARA TUS UNDERWATER HEAT SINK STATEMENT OF GOVERNMENT INTEREST The invention described herein may be manufactured and used by or for the Government of the United States of America for Governmental purposes without the payment of any royalties thereon or therefor.

FIELD OF THE INVENTION This invention relates generally to underwater breathing apparatus of the type known as cryogenic, in that the breathing gas is derived, in whole or part, from liquified gas, e.g., liquid air or liquid oxygen carried at very low temperatures in a reservoir. More particularly, the invention is directed to an underwater, cryogenic heat sink, in combination with such breathing apparatus. for maintaining a substantially constant low temperature circuit in the liquified reservoir, whereby a number of operational advantages can be achieved.

DISCUSSION OF THE PRIOR ART Among the virtues that are common to cryogenic divers breathing apparatus, or life support systems, is the ability to carry a large quantity of oxygen, air, or other oxygen/gas mixture in liquid form at relatively low pressures, thereby avoiding the need for heavy, potentially dangerous, high pressure flasks carrying compressed gases. Typically, the known cryogenic diving apparatus carries a supply of liquid oxygen, air, or other mixture, in an insulated flask, or Dewar, and utilizes boil off therefrom for a breathing gas supply at a pressure only slightly different from the ambient water pressure at the particular depth at which the diver is working. A substantially constant predetermined pressure with respect to ambient pressure has been maintained in such systems by venting the excess boil off, through suitable pressure responsive valves, to the ambient water medium. Examples of these systems are found in US. Pat. No. 3,366,107 to R. L. Frantom, US. Pat. No. 3,570,481 to J. W. Woodberry, and US. Pat. No. 3,572,048 to R. H. Murphy. Because the water pressure and temperature conditions can vary considerably from point to point during a dive, and since the divers oxygen consumption rate varies considerably with work and depth, the prior art systems have been calculated to permit boil-off from the liquifred gas supply at the maximum rate possibly needed under the most severe circumstances, with no provision for controlling the rate of boil-off.

The result has been wasteful of the liquified gas supply, thereby shortening the duration of dive, and has prevented the achievement of a fully closed, bubblefree system. Obviously, conservation of the liquid breathing gas supply is logistically desirable, while a bubble-free system is advantageous for covert military operations, as well as to be free of the noise and reduced visibilityoften created by escaping bubbles.

Moreover, it is 'well understood that the partial pressure of oxygen that is required in a breathing gas mixture to properly sustain a diver must stay relatively constant as depths increase. The problem of regulating this partial pressure of the oxygen in a cryogenic system, as well as the previously mentioned disadvantages, can be eased considerably by maintaining the liquid oxygen reservoir at a predetermined temperature, e.g.,

-2l3F, by extracting heat therefrom as necessary to accomplish this. Heretofore, no known apparatus has been available that could be easily carried by a diver as part of a self-contained breathing apparatus, would operate to maintain a selected low temperature in a liquid oxygen reservoir thereof irrespective of ambient pressure changes, and would do so without itself generating bubbles and requiring power consuming equipment such as pumps.

SUMMARY OF THE INVENTION The present invention aims to overcome the mentioned disadvantages or shortcomings of the prior art, as well as others, through the provision of a cryogenic heat sink that serves to maintain the temperature of a liquid oxygen or other Iiquified medium in a reservoir,

at a predetermined temperature irrespective of ambient pressure changes.

With the foregoing in mind it is an important object of the invention to provide a cryogenic heat sink that is operable, in an underwater environment, in conjunction with a cryogenic breathing apparatus.

Another object is the provision of a cryogenic heat sink that is characterized as a closed system in that it utilizes evaporation from a body of liquified gas to extract heat from the matter to be cooled or temperature regulated, and an accumulator or adsorbing means for maintaining a predetermined reference pressure in the heat sink system.

Still another object is the provision, in an improved cryogenic breathing apparatus for underwater use, of a heat sink of the foregoing character that comprises a pressure responsive valve means between the body of liquified gas and a relatively low pressure zone in which the adsorbent material is disposed, and valve means being responsive only to the absolutepressure'of the vapor over the liquified gas and operative to pass vapor to the low pressure zone whenever the absolute pressure of the vapor exceeds the pressure of equilibrium for a selected temperature to be maintained in the body of liquified gas and its vapor.

Other objects and many of the attendant advantages will be readily appreciated as the subject invention becomes better understood by reference to the following detailed description, when considered in conjunction with the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a diagrammatic illustration of cryogenic underwater heat sink apparatus embodying the invention;

and 1 FIG. 2 is an enlarged sectional view of a regulating valve forming part of the apparatus of FIG. 1.,

DESCRIPTION OF THE PREFERRED EMBODIMENT wall 26. Chamber 24 contains a quantity of liquified 3 gas, liquid oxygen 28 in the present example, the purpose of which will be made apparent as this specification proceeds. Immediately above heat exchanging wall 26, and below a wall 30, is a chamber 32 in tank that serves as a reservoir for containment of a quantity of liquified gas, liquid oxygen 34 in the present example.

Above wall 30, and below an end closure wall 36, the interiorof tank 20 is divided by a heat exchanging wall 40 into chambers 42 and 44 which communicate with chamber 32 through openings 46 and 48, respectively, in wall 30. Chamber 42 also communicates, through a gas supply duct 50 with a divers breathing apparatus 52, while chamber 44 communicates with that apparatus through a gas return duct 54.

The apparatus 52 may be of conventional construction, preferably of the type comprising means for conveying breathing gas to and from a divers mouth, adsorption means for removing carbon dioxide and moisture from expired gas, a supply of relatively inert gas, such as helium, and suitable valve means for maintaining the breathing gas mixture in the apparatus at a pressure appropriate for breathing under the different ambient pressures existing at the depths to which the using diver descends. Additionally, the apparatus 52 may comprise other devices common to such apparatus such as breathing bag means for accommodating the changes in volume attendant respiration, oxygen content 'or partial pressure sensors, and the like. The apparatus 52 with which the invention is associated may be diver carried, may form part of a submersible vehicle, or may be part of an underwater habitat.

The upper part of liquid oxygen and vapor containing chamber 24 is connected to a duct 60 that extends upwardly through chambers 32 and 44 to the exterior of tank 20. Chamber 24 is adapted to communicate, through duct 60, a pressure regulating valve 62, and a duct 64, with a bed of oxygen adsorption material 66 contained in a pressure resistant tank 70. Valve 62, which will be discussed in more detail with reference to FIG. 2 and in the subsequent description of the mode of operation of the invention, serves to maintain a predetermined pressure in chamber 24, irrespective of ambient pressures.

Oxygen adsorption material 66 may comprise any one of various well known and commercially available materials, such as activated charcoal. Of course, some materials are more efficient than'others in performing the function of adsorption of oxygen (or absorption as the case may be), and one commercial product that has been found particularly good is that sold as a molecular sieve material by Union Carbide Corporation in the form of that company's Molecular Sieve Type 4A Pellets. Under proper temperature and pressure conditions, that material is capable of adsorbing approximately twenty pounds of oxygen for each hundred pounds of adsorption material. The amount of material 66 in tank 70 is preferably sufficient to adsorb all of the oxygen with which the chamber 24 is charged at the beginning of operation.

Referring now to FIG. 2, valve 62 comprises a body 74 having chambers 76 and 78 disposed on opposite sides of a flow passage 80. Passage 80, which connects at one end with duct 60 and at the other end with duct 62, is interrupted by a bore 82 extending from chamber 76 to chamber 78. A valve member 84 is reciprocable in bore 82 and is characterized by an annular groove 86 that is movable into and out of registry with passage 80 to control flow between ducts 60 and 62.

A tension spring 90 in chamber 78 acts, between body 74 and a valve member 84, to urge the latter toward a valve closed position in which flow through pas.- sage 80 is prevented. A sealed, evacuated bellows 94 is disposed in chamber 76 and acts, between body 74 and valve member 84, in opposition to spring 90. The use of an evacuated bellows renders valve 62 substantially insensitive to temperature changes.

Chambers 76 and 78 are respectively connected by passages 96 and 98 to passage 80, and hence to duct 60 and the interior of chamber24. It will be apparent that the effective area of bellows 94 that is responsive to pressure changes in chamber 76 is greater than the effective area of valve member 84 that is responsive to corresponding pressure changes in chamber 78. Accordingly, the valve member will seek a'balanced position where the excess force exerted by bellows 94 is equalled by the force of spring 90. A spring 90 is selected that will result in valve 62 being closed whenever pressure in chamber 24 is less than a predetermined pressure, and opened whenever the pressure in chamber 24 exceeds that pressure. In the present example that pressure is 0.38 atmospheres, or approximately 5.59 psia. Flange 84a limits movement of valve member 84 to a predetermined open position.

It will be understood, of course, that the portions of tank 20 defining chamber 24, tank 70, ducts 60 amd 64, and valve 62 must be sufficiently rigid to withstand considerable excesses of external pressure without collapse.

MODE OF OPERATION Consider the chambers 24 and 32 to have been appropriately precooled and to be charged with a quantities of liquid oxygen 28 and 34, respectively, at a temperature of-2l 3F, and the tank to be charged with oxygen adsorbing material 66 such as the mentioned molecular sieve material. Recall that one of the principal objects of the invention is to maintain the temperature of the liquid oxygen 34 at a predetermined temperature, say 2l3F, irrespective of ambient pressure changes thereon. Now, breathing gas, at a temperature substantially above that of liquid oxygen 34 in chamber 32, is caused to pass from apparatus 52 through duct 54, chamber 32, chamber 42, and return by duct 50 to apparatus 52. Some ofliquid oxygen 34, warmed somewhat by the passing breathing gas, vaporizes to increase the oxygen content of the breathing gas.

Additional heat energy, tending to warm liquid oxygen 34 in chamber 32, passes from surrounding waters through the insulated walls 22 of tank 20, and results from the increase in total pressure within chamber 32 as the apparatus is moved to greater water depths. Re-

moval of sufficient heat from liquid oxygen 34 is accomplished in accordance with this invention by maintaining in chamber 24 a constant, low pressure that will allow liquid oxygen 28 to seek equilibrium between liquid and vapor states at the desired temperature of --2 l 3F, thereby serving as a heat sink to which thermal energy can flow from liquid oxygen 34 through heat exchange wall 26 whenever the temperature of the latter exceeds -2 l 3F.

In accordance with the known physical properties of liquid oxygen, if oxygen vapor is removed as necessary from chamber 24 to maintain a low pressure of 0.38 atmosphere, the temperature of the remaining oxygen will hold constant at -2 l 3F. The action of the oxygen adsorbent material 66 in tank 70 is effective to reduce the pressure in that tank, and in duct 64, to a value considerably below 0.38 atmosphere. Regulating valve 62, interposed between chamber 24 and tank 70, serves to vent to tank 70 any pressure in excess of the required 0.38 atmosphere in chamber 28. Because the quantity of adsorption material 66 is sufficient to take up all of the oxygen with which chamber 24 is initially charged, the desired constant temperature will be automatically maintained until the liquid oxygen 28 is depleted.

lt will be recognized that the operation of the heat sink embodying the invention is wholly independent of ambient pressures and temperatures, the regulating valve 62 serving as the sole reference for pressure in the chamber 24 and the resulting temperature that is maintained therein.

Obviously, other embodiments and modifications of the subject invention will readily come to the mind of one skilled in the art having the benefit of the teachings presented in the foregoing description and the drawings. lt is, therefore, to be understood that this invention is not to be limited thereto and that said modifications and embodiments are intended to be included within the scope of the appended claims.

What is claimed is:

l. A cryogenic underwater breathing apparatus of the type wherein liquified gas is allowed to vaporize to augment a breathing gas mixture, said apparatus comprising:

a first tank including insulated wall portions in part defining first and second adjacent chambers, said first tank also including heat exchange wall means between said first and second chambers and means for circulating breathing gas through said first chamber;

a body of first liquified gas in said first chamber substantially at a predetermined low temperature;

a body of second liquified gas in said second chamber also substantially at said predetermined low temperature;

means defining a third chamber;

adsorption material disposed in said third chamber and adapted to reduce pressure therein below a predetermined equilibrium pressure for said second liquified gas at said predetermined temperatures;

a pressure responsive regulating valve;

duct means connecting said pressure responsive regulating valve between said second and third chambers; and

said pressure responsive regulating valve being responsive only to gas pressure in said second chamber and operative to vent gas from said second chamber to said third chamber, so as to maintain said equilibrium pressure and said predetermined low temperature.

2. A cryogenic underwater breathing apparatus as defined in claim 1, and wherein said regulating valve comprises:

a valve body having a flow passage connected at one end to said second chamber and at its other end to said third chamber, said body defining fourth and fifth chambers on opposite sides of said flow pas- 6 sage and communicating only with said one end thereof; a valve member disposed between said ends of said flow passage and movable between open and closed positions with respect to said flow passage; spring means disposed in one of said fourth and fifth chambers and operative to urge said valve member toward one of said positions; and

pressure responsive actuating means disposed in the other of said fourth and fifth chambers and operative to urge said valve member toward the other of said positions.

3. A cryogenic underwater breathing apparatus as defined in claim 2, and wherein:

said first and second liquified gases e ach comprise liquid oxygen, and said adsorption material comprises a molecular sieve material.

4. A cryogenic underwater breathing apparatus of the type wherein liquified gas is allowed to vaporize to augment a breathing gas mixture, said apparatus comprising:

a first tank including insulated outer walls, said tank includingfirst and second chambers separated by heat exchanging wall means, and additional wall means .for guiding circulating breathing gas through said first chamber;

a body of liquified gas in said first chamber at a predetermined low temperature;

a body of second liquified gas in said second chamber also substantially at said predetermined low temperature; t

a second tank defining a third chamber;

adsorption material disposed in said third chamber and adapted to adsorb vapor of said second liquified gas and to reduce pressure in said third chamber below a predetermined equilibrium pressure for said second liquified gas at said predetermined temperature;

a pressure regulating valve;

duct means connecting said pressure regulating valve between said second and third chambers;

said pressure regulating valve comprising a valve body having a flow passage connected at one end thereof by said duct means to said second chamber and at the other end thereof to said third chamber, said body defining fourth andififth chambers on opposite sides of said flow passage and communicating only with said one end thereof, a valve member disposed between said ends of said flow passage and movable between open and closed positions with respect to said flow passage, spring means disposed in said fourth chamber and operative to urge said valve member toward one of said positions, an expansible and contractable bellows disposed in said fifth chamber and operative upon predetermined pressure change in said second chambers to move said valve member toward the other of said positions, whereby said pressure regulating valve is ambient pressure independent and operative to vent gas from said second chamber to said third chamber so as to maintain said equilibrium pressure and said predetermined low temperature therein. 

1. A cryogenic underwater breathing apparatus of the type wherein liquified gas is allowed to vaporize to augment a breathing gas mixture, said apparatus comprising: a first tank including insulated wall portions in part defining first and second adjacent chambers, said first tank also including heat exchange wall means between said first and second chambers and means for circulating breathing gas through said first chamber; a body of first liquified gas in said first chamber substantially at a predetermined low temperature; a body of second liquified gas in said second chamber also substantially at said predetermined low temperature; means defining a third chamber; adsorption material disposed in said third chamber and adapted to reduce pressure therein below a predetermined equilibrium pressure for said second liquified gas at said predetermined temperatures; a pressure responsive regulating valve; duct means connecting said pressure responsive regulating valve between said second and third chambers; and said pressure responsive regulating valve being responsive only to gas pressure in said second chamber and operative to vent gas from said second chamber to said third chamber, so as to maintain said equilibrium pressure and said predetermined low temperature.
 2. A cryogenic underwater breathing apparatus as defined in claim 1, and wherein said regulating valve comprises: a valve body having a flow passage connected at one end to said second chamber and at its other end to said third chamber, said body defining fourth and fifth chambers on opposite sides of said flow passage and communicating only with said one end thereof; a valve member disposed between said ends of said flow passage and movable between open and closed positions with respect to said flow passage; spring means disposed in one of said fourth and fifth chambers and operative to urge said valve member toward one of said positions; and pressure responsive actuating means disposed in the other of said fourth and fifth chambers and operative to urge said valve member toward the other of said positions.
 3. A cryogenic underwater breathing apparatus as defined in claim 2, and wherein: said first and second liquified gases each comprise liquid oxygen, and said adsorption material comprises a molecular sieve material.
 4. A cryogenic underwater breathing apparatus of the type wherein liquified gas is allowed to vaporize to augment a breathing gas mixture, said apparatus comprising: a first tank including insulated outer walls, said tank including first and second chambers separated by heat exchanging wall means, and additional wall means for guiding circulating breathing gas through said first chamber; a body of liquified gas in said first chamber at a predetermined low temperature; a body of second liquified gas in said second chamber also substantially at said predetermined low temperature; a second tank defining a third chamber; adsorption material disposed in said third chamber and adapted to adsorb vapor of said second liquified gas and to reduce pressure in said third chamber below a predetermined equilibrium pressure for said second liquified gas at said predetermined temperature; a pressure regulating valve; duct means connecting said pressure regulating valve between said second and third chambers; said pressure regulating valve comprising a valve body having a flow passage connected at one end thereof by said duct means to said second chamber and at the other end thereof to said third chamber, said body defining fourth and fifth chambers on opposite sides of said flow passage and communicating only with said one end thereof, a valve member disposed between said ends of said flow passage and movable between open and closed positions with respect to said flow passage, spring means disposed in said fourth chamber and operative to urge said valve member toward one of said positions, an expansible and contractable bellows disposed in said fifth chamber and operative upon predetermined pressure change in said second chambers to move said valve member towaRd the other of said positions, whereby said pressure regulating valve is ambient pressure independent and operative to vent gas from said second chamber to said third chamber so as to maintain said equilibrium pressure and said predetermined low temperature therein. 